Full Moon (Even Super-Duper Full Moon)? No Problem!

My foray into Hα imaging using an inexpensive one-shot color camera continues. One of the things proponents of narrowband imaging usually mention is that you can do it from heavily light polluted skies and even when the Moon is full. My light pollution isn't horrible (technically, according to the light pollution maps that go with the clear dark sky charts, I'm in a Bortle orange-yellow transition area), but the Moon was definitely full last night. It was even the brightest so-called "super Moon" of the year (a few percent larger and brighter than normal because full Moon occurred at perigee this month). Anyway, over the last 2 nights I've been testing my ability to do Hα imaging under bright sky conditions, and it does work. So far, I'm continuing to stick to using a focal reducer to speed up my optics and to make the guiding very forgiving (we keep having gusty wind every night, so I need it to be forgiving).

Here's the Crescent Nebula in Hα from a couple of nights ago. Even under cloudy, hazy conditions it turned out OK I think. Conditions were terrible: a very bright Moon (which really doesn’t matter for Hα but matters for finding things) and lots of clouds combined with lots of haze. I tried to start on the Elephant's Trunk Nebula but could not find any asterisms nor could I see it after 300 s) so I came back to the Crescent where I knew I could see the parallelogram of stars. It was even a little bit difficult to find Sadr to sync (clouds and haze being the main culprit). 600 s subs are still barely sufficient. Warm; started at 24.5 °C and the chiller got it down to about 14-17 °C (it was drifting down through the night). Did a meridian flip and continued. The power of Hα is evident in that I got anything useful out of such poor conditions. It will be nice to get some Hα on a good night!

Date: 8 Aug 2014

Subject: NGC 6888, Crescent Nebula

Scope: AT8IN+0.5x Antares telereducer

Filter: Baader Planetarium 7 nm H-α

Mount: CG-5 (Synta motors, PicGoto Simplificado)

Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.3.0 (Win 7 ASCOM)

Camera: DSI IIc chiller at 2.50 A, 14-17 °C

Acquisition: Nebulosity 3.2.0, no dither

Exposure: 23x600 s

Stacking: Neb 3, bad pixel map, bias included, extract R, resize 2x, normalize, trans+rot align, 1.5 SD stack.

Processing: StarTools 1.3.5.279 Crop; Wipe:Color & brightness 75%; Develop 74.99%; HDR:Optimize; Deconvolute 2.7 pix; Life:Moderate; Track RNC 0.25%; Magic:Shrink 1 pix.  CS6 AstronomyTools B&W to Hα; layer masked deep space, space noise reduction; Astro Frame.

I'm having a terrible time trying to do HαRGB or HαRRGB combinations with this. The problems come with replacing the RGB R channel. The Starizona method says you should combine Hα with an extracted R and use that to replace R. However, that always seems to leave the resulting RGB quite blue, especially the stars. I don't know how to fix it. Part of the problem may be that in this particular case my RGB is really not full RGB, it was taken through a UHC-S nebula filter. Anyway, here's the best so far. I'm not sure it's any better than the RGB I started with.

Hα of the Bubble Nebula turned out pretty well; it's my best Bubble so far. Full Moon (in fact Super Duper Moon if you believe the media!). You really can do this Hα stuff under a full Moon. There's still lots of haze in the air, but when I went out to check the sky, things looked good enough to try so I did (besides, I left my gear out from the night before so I didn't have to set up!). There was also quite a bit of gusty wind again. Anyway, the Bubble was easy to find from α Cas with the PicGoto and easy to recognize even with short exposures of a couple of seconds even with the filter. 2.5 A on the chiller has the CCD at 16 °C. I like the way the filter picked up lots of detail in the nebula and a lot of surrounding gas I couldn't pick up otherwise. And all this under the Moon as full as it gets.

Date: 9 Aug 2014

Subject: NGC 7635, Bubble Nebula

Scope: AT8IN+0.5x Antares telereducer

Filter: Baader Planetarium 7 nm H-α

Mount: CG-5 (Synta motors, PicGoto Simplificado)

Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.3.0 (Win 7 ASCOM)

Camera: DSI IIc chiller at 2.50 A, 16 °C

Acquisition: Nebulosity 3.2.0, no dither

Exposure: 24x600 s

Stacking: Neb 3, bad pixel map, bias included, extract R, normalize, square, trans+rot align, 1.5 SD stack, resize 2x,.

Processing: StarTools 1.3.5.279 Crop; Wipe:Color & brightness 75%; Develop 70.97%; HDR:Equalize; Deconvolute 2.7 pix; Life:Moderate; Track RNC 79.41%; Magic:Shrink 1 pix.  CS6 AstronomyTools deep space noise reduction; B&W to Hα; Astro Frame.